Coated abrasive article



Patented Jan. 6, 1942 e,

- UNITED STATE S PATEN T OFFICE coA'rsn A'naAsIvE ARTICLE George P. Netherly and Bert 8. Cross, St. Paul,

Mint, and Gilbert B. Anderson, Wilmingto DeL, assignors to Minnesota Mining .1; Mannfacturing Company, St. Paul, Minn, a corporation of Delaware No Drawing.

Application M112, 1941,

(01. 51-2) This application is a continuation-in-part of 1 3 Claims.

our copending application Serial No. 179,338,

L support.

The invention is particularly directed to the coating of supports such as strips or sheets oi.

- fabric, paper, or'the like, with abrasive particles or granules and the application of their securing means for. adherence thereto to make abrasive articles.

Composite structures of the abrasive type such as sandpaper or emery cloth comprise generally, '(a) a base of sheet material, which may be felted as in the case of paper or woven as in the case of cloth, (b) a more or less finely comminuted resistant material having abrading properties, such as garnet, corundum, or the like, and (c) a binder generally in the form of a glue or resinous bond which serves to bind the abrasive to the The manufactured abrasive articles known to' us have at no time in the past ever been made so that all abrasive particles are coated and held" in a durable matrix of solidified adhesives in such a manner that substantially all of the particles have an opportunity of rendering full utility.

The abrasive particles, to be firmly secured,

require an additional bond ora plurality of bonds to anchor them to the adhesive on which they are coated. This additional bonding gives the finished abrasive article additional strength and utility, but in so doing, and in the methods .of present use and their adaptation, agreatperidentage' of the orientation and perpendicular erection of the abrasive particles is destroyed.

manner'that the longer dimensional configuration of the granular material is placed approximately P rpendicular to the bond. Present methods of applying oriented particles are amply illustrated by electrostatic means as described in the patent to J. S. Bmyser, No. 1,788,600.

our invention is not concerned with the prob lems of applying the abrasive particles in a particular manner to the base material, but is concerned primarily with the provision or a combination of individually distinct and separate adhesive coatings co-operatively maintaining the particles in the original position obtained in their first application to the base. preferably such that the particles are oriented so that a substantial proportion of their pointed abrasive surfaces are exposed, or at least such that particles are disposed with the long dimensions'thereoi' at a substantial angle to the base.

ules in an oriented position for the purpose of producing maximum shearing efiect of the working' article. By orientation of an. abrasive granule,'we mean a disposition of the granular material coated on a bonding surface in such a It is therefore a principal object of this invention to secure a maintenance of orientation of abrasive particles adhering to a primary or making adhesive coated on a base, during and after. application of a second anchoring adhesive coating; 1

3 Another object of this invention is to provide anabrasive article having a better cutting edge due'to coating of the particles in such a manner as to maintain them in an oriented position throughout the finishing process.

'A further object is to provide for maintaining orientation of the abrasive particles on abrasive articles both as to those having a substantially rigid backing and those having a flexible backing; and the invention is applicable to preparing abrasive articles both for dry abrasive work and wet abrasive work.

In addition, we have further found that the application of the bonding materials in accordance with our invention results in an abrasive article having increased life .and durability, as well as a strengthened granular bond.

In accordance with the; present invention, the primary or making coat oi adhesive (upon which the 'comminuted solid material is deposited as a layer or coating), and the second anchoring or sizing coating of adhesive (applied after the comminuted solid material), are of such nature with respect to eachv other 'as to prevent the application of the anchoring binder coating from loosening the bond between the primary adhesive and the comminuted material. However, after application of some of the type, adhesives as hereinafter expressed, a slight softening eil'ect may be produced by heat treatments or the like, tending This position is to fuse the bonds Such slight softening efiect tion, claimedherein and described more in detail hereinafter, the abrasive bonding or binder coat may be an inorganic material and the sizing coat may be an organic material, or vice versa. For example, the binder coat maybe a cement, such as a hardened sodium silicate cement over which is placed a sizing coat of an organic material such as a vinyl acetal or other vinyl resin, an oil-modified alkyd resin, a heat-convertible resin (e. g. an oil-reactive or oil-reacted'phenol aldehyde or straight phenol aldehyde), a urea aldehyde resin, etc. Such asizingserves, among other things, to keep carbon dioxide away from the silicate coating. Where greater flexibility of the binder coat'is desired, this may be accomplished in several ways, e. g. by adding casein or the like, rubber latex, etc., to the aqueous silicate in desired amount.

The nature of the invention willbe apparent in more detail from the following examples and descriptions by which it is illustrated:

l. A glue-resin adhesive is made up consisting of Parts Glue '74 Phenol aldehyde resin. 82 Water 66 Urea L 13 Concentrated ammonia 24 Cellosolve (ethylene glycol monoethyl ether) 16 This adhesive composition is coated on a backing material such as cloth, paper, or the like, as the primary or making coat. Abrasive granules are then oriented or coated on this adhesive and i left to dry at room temperature for approximately 20 minutes. The sheet so dried is then coated with a 'phenol aldehyde resin solution.

which consists of:

. Parts Phenol aldehyde resin 60 Cellosolve 40 again dried as above. The solvent Cellosolve" used in this second anchoring adhesive has no effect on the primary bond to the extent of causing the abrasive mineral to lose its oriented position, the primary bond having been insolubilized to any mono-constituent solvent by evaporation of the solvents water and Cellosolve.

2. Another example of the'use of this principle of coating is to insolubilize a coating of adhesive through direct chemical reactions, such as by a tanning reaction, or by heating. In this case, for example, a coating of glue of the usual type is applied to the abrasive backing'and then the abrasive material is coated to the adhesive- The glue coated backing with abrasive thereon is then passed into a formaldehyde gas filled chamber wherein the glue is converted from a film soluble in water to one insoluble in water. -A second coating of glue is then applied as an anchoring means for securing the abrasive material over the oxide, stannous chloride, .hexamethylenetetramine, or the like,,any and all of which will-render' the adhesive substantially water-insoluble and weather-resistant. The. anchoring bond subsequently added has no. efiect on the original.

' position of the mineral particles because the solvent of the second coating does not aflect thev primary securing means. To render the anchoring bond water-insoluble, the article may again be passed into the formaldehyde chamber or be otherwise treated as heretofore mentioned.

3. Similar results are obtained where a resin, for example a phenol aldehyde or heat-advancing resinsoluble in the alcoholsv as methyl and the like or ketones as acetoneor organic esters. as ethyl acetate, etc., is used as aprimary coat on .a backing. The mineral is coated directly on the original glue film. In place of the specific formaldehyde gas there may be substituted para formhesive may be mixed with or treated after aptannic acid or its salts,

plication in a bath of chrome alum, sodium dipicrlc acid or its salts,

chfomate, dichromic acid or its salts, titanium ll adhesive phenol aldehyde surface. Sufllcient heat is then directed on-the mineral coated backing to volatilize the solvent and polymerize the resin. The temperature employed generally will run from 150 F. to 225 F. or higher as applicable to the materials used. The time varies from 20 minutes to several hours depending upon the amount of resin coated and the temperature used. Having accomplished a partial polymerization of the resin, we are then able to add additional resin in the form of an anchoring adhesive without affecting orientation because the resin once properly set up will not be further-aflectedby the solvents in the anchoring coat, with alike treatment to set up this anchoring means. The subsequent heating may slightly interfuse the interfacial surfaces of this type bond without a destruction of the granular positioning.

4. Another example of the type bonding materials which we propose using is a primary adhesive coating applied as a base or binder ior= disposition of abrasive granular mineral, for example glue and resin soluble, e. g. in alcohol and water, which can be, by heat treatment as is commonly known to the trade, hardened sufllciently to hold the granules in place, and then a coating of a resin such as Bakelite, or other phenol aldehydes or heat-advancing resins, or styrene, vinylite resins and the like, which con tains no solvent and is normally liquid at room temperature, is applied over the granules and the coated article is then subjected to a temperature which will polymerize or set up the resin beginning at approximately Rand not exceeding the limit at which carbonization takes place. i

5. Other methods of accomplishing a maintenance of orientation include use of a hydrophilic primary casein binder adhesive and an I example, byheat and pressure, light, or a catalyst such as oxygen or a peroxide. An additional illustration is the application of a phenol aldehyde resin soluble in ethylene glycol monoethyl ether which serves as a good primary coating and maintains orientation well when employed in conjunction with N-propyl methacrylate polymer solution' in benzene used as an anchoring ad'-*' hesive.

In addition to the above enumerated examples, use may be made of an anchoring adhesive-('sufcl'r as a resin) in an organic solvent, which maybe any ketone, poly ether, ester, ethyl alcohol,v

- made by sealing layer (such as i'rom attacking the methyl alcohol, furfurane derivative, any chlo- By the methods as herein disclosed, the pri-' rinated solvent or any other "organic solvent or mixture of organic solvents, ineconjuncti'on with a primary binder adhesiveor bond'dissolved inwater, but not soluble in the particular solvent used in the anchoring adhesive." Conversely, we,

may make use of an anchoring adhesive dissolved in water and a water-insoluble primary binding bond dissolved in an organic solvent as of the above character. These possibilities are illustrated by the use of a blood albumin anchoring adhesive in water; and a primaryresin binder j adhesive soluble in- 'a hydrocarbon oi the above character; by a primary casein glue binder adhesive in water and a resin anchoring adhesive in an organic solvent, such as ether alcohols, esters, and the like, in which the glue is insoluble;

and by water-soluble soybean protein glue or ani"-..

I combinations of adhesives may be applied ior'the.

mal glue as the primary binder adhesive and a phenol aldehyde or other ,resin anchoring means in an organic solvent, such as benzene, ether;

alcohol and the like, in which the protein or glue is insoluble; any and all of which coatings may be used in vice versa or interchangeable form as contemplated by this improved combination of bonding means,

The phenol aldehyde or other resin size may advantageously be applied, as a liquid, or as a solution in a volatile solvent, over the'glue or like binder after the. glue has gelled and before I it has dried out, e. g. within 5 to 20 mintes, more or less, after abrasively coating the gluebinder.

Further, by way oiillustration, we may use an anchoring adhesive dissolved in an organic solvent and a primary binder bond dissolved in another organic solvent, but not soluble in the-particular solvent used in the anchoring adhesive. as an example of this type of bonding means, in addition to those already given, we may use a primary binder coating of a proteide type, such as zein or the like, in alcohol, and a resin anchoring coating having an organic solvent in illustrated in any mary binder and anchoring coats are co-operatively distinct in the product, although adhering or bonded together at'the interface without destroying the granular position.

In general, it is ourrdesire to use-the examples plish the pu p of stitutes v thereof which by nature have charac-' teristics for accomplishing the results'herein de-' scribed; and while weihave described more or less specifically the application of certain coatings, it will be readilyunderstood that other purpose of securing maintenance of orientation. What we claim is: 1. Acoated abrasive sivegrainssecured to a backing by a plurality of coatings of bonding materials'including a pri m'ary. bonding coating and a sizing coating, said abrasive grains being positioned in said bonding coating in predetermined oriented relation to said backing andwre'iniorcedc and substantially maintained in said predetermined position by said sizing coating, said bonding coating being or a material selected with respect to the material of said sizing coating such as to be substantially unsoftened and undissolved by the material 01' said sizing coating in fluid iorm, one of said coatings comprising an organic gelatinous adhesive material andthe other of said coatings comprising an inorganic siliceous material. 1

2. A coated abrasive-article comprising abra- 1 sive grains secured to a backing by a plurality or I coatings of bonding materials including a pri-. mary bonding coating and a sizing coating, said abrasive grains being positioned in'said bonding which the primary binder is insoluble such as benzene, ether, chlorinated methane, and the like.

As an alternative method of applying coatings dissolved in the same solvent, we have found that we may. apply the granules to a rimary adhesive coating and then by the use or a thin interposed.

. with the addition or this thin coating and sealing material, we have inre'ality applied three mms ior securing the abrasive granules and find that it is possible, by the use oi the intermediate that previously mentioned,

- cludinga primary a sizing coating, said maintained in such position by or any equivalent layer which-will meet the'requirement's or preventing the anchoring coating primary or making coat and 01 securing a good intermediate cohesion between the making and the'sizing bonds), to inter-' changeably use the bonding means in'any term or combination desired. whether dissolved in a like solvent or not. 4

coating in predetermined oriented relation to said backing and reiniorced and substantially maintained in said predetermined position by said sizing coating, said bonding coating being or a material selected with respect to the material of said sizing coating such as to be substantially f unsoftened and undissolved' by the material 015, said sizing coating in fluid.iorm,.said binder or bonding coat comprising a silicate and said sizing coat comprising an organic resinous material.

3. A heat-resistant coated abrasive article comprising abrasive grains secured to a backing. by a plurality or coatings ofbonding bonding or binder coating and abrasive grains being positioned in said coating so that .a substan-' tial percentage of said grains have thelong dimension thereof approximately perpendlcularto reinforced andsubstantially said sizing coating, said bonding coating being of a material selected with respect to the material or said sizing coating such as to be substantially unsoitened and undissolved by the material oisaid sizing coat in fluid form, 'said binder coating comprisim a hydrophilic organic adhesive material and said sizing coating being a non-thermoplastic waterinsoluble adhesive material.

, GEORGE P. ua'rnnatr.

near 5. caoss onnea'r a. aunretsou,

said backing and combination which will accomour invention, or any sub-' article comprising abramaterials in- 

